Method of refining alloys



Patented 4, 1934 UNITED s'rA'rEs METHOD or name ALLOYS August Kuhlmann,Falls, N; Y., as-

signer to Electra Metallurgical Company, a corporation of West VirginiaNo Drawing.

tion June 4, 1932,

Appliea Serial No. 615,469

1 Claim. '(CI. 75-11) My invention relates to the refining of certainalloys containing aluminum, and refers more specifically to the removalof aluminum from such alloys by a novel refining process,

"8 The chief object of the invention is to provide a novel processwhereby high aluminum alloys, such as those produced by thealuminum oralumino-thermic reduction of refractory corn- P unds of metals, berefined to low alumilu num'or aluminum free alloys effectively andefficiently.

In the production of metals and alloys from refractory ores andcompounds by aluminum or alumino-thermic reduction, it is usually advan-1'5 tageous to operate with a considerable excess of aluminum in orderto efiect a good recovery of metal from the compound. When using suchexcess of aluminum; it is frequently difiicult to produce an alloyhaving a low aluminum conao tent, for some of the aluminum alloys withthe metal or metals being reduced, or even forms metallic compoundstherewith. The usual methods of refining out the excess of aluminum withoxygen-containing compounds are often uncerz's tain in result, andinvolve large losses of one or more of the alloying elements.

Ihave discovered that many high aluminum alloys may be refined and thealuminum content thereof lowered or even completely removed so if themolten alloy is treated with a metal sulphide selected from a group ofmetals which have less chemical aflinity for sulphur than has aluminum.I have further discovered that the I additions of metal sulphide mayreadily be'made as so as controllably to reduce the aluminum content toany desired amount without introdu a detrimental amount of sulphur intothe alloy.

Thehighaluminumalloystowhichtheprocass is applicable include those ofallmetalshav- .a'o'ing a lower chemical afilnity for sulphur than hasaluminum. For instance, alloys containing iron, cobalt, nickel, copper,silver, boron, chromium, tungsten, molybdenum, silicon, tantalum,

columbium, uranium, and vanadium alloyed with 8. aluminum either singlyor in various combinations are included.

,The metal sulphide used in the refining process may be any within theabove definition; that H is, any metal sulphide is suitable wherein theso metallic constituent has a lower chemical aiilnity sulphur than hasaluminum, such for examiron sulphide, or chromium sulphide. It

be dmirable to use a sulphide of on furnace conditions and temperatures.

like ferroboron, or chromium sulphide in the case of a chromium-boronalloy; but wherever the introduction of a foreign metal other thanaluminum is.unobjectionable, sulphidesof metals other than the chiefconstituents of the alloy may be used. The choice of a particularsulphide will be governed mainly by the above requirementas to chemicalaffinity, by the desired constitution and purity of the refined product,and by considerations of cost.

The process of the invention may be carried out by smelting a mixture ofthe high aluminum alloy and the proper sulphide in an electric or otherfurnace. However. any method which brings the said alloy and thesulphide into reaction' may be considered as within the scope of thepresent invention; for instance, the high aluminum alloy may be refineddirectly as it is produced in the. reduction process, by treating thestill molten alloy with a molten bath containing the desired sulphide.

The reaction between the metal sulphide and the aluminum contained inthe high aluminum alloy being refined. results in the liberation of themetal constituent of the sulphide and in the g formation of aluminumsulphide. In general, no other fluxing agents are required, the aluminumsulphide forming a fluid slag. Other slag forming materials such aslime, silica, alumina, and the like may be present, however, and inlimited as quantity are not detrimental :to the process. The proportionof metal sulphide to be employed will depend on the amount of aluminumit is desired to remove from the alloy. In general, a quantity of metalsulphide slightly less than the stoichiometrical amount shown by thefollowing typical reactions should be employed.

Slightly less than the theoretical requirement is used, for incommercial furnaces some oxidation of aluminum by air is inevitable.However, when a sulphide is employed which may be ther- 100 mallydecomposed at the furnace temperatures, such as, for instance, ironpyrites (Fess) somewhat more than the stoichiometrical requirement mustbe used, depending to a large degree As an example of the application ofmy invention the following is typical: 775 pounds of crude ferroboroncontaining 81.08%v of boron,

' 383896; of aluminum,.the remainder to make up beingmostlyi-ron.wassmeltedinanelec- 110 tric iurnace together-with 175' pounds oi. ironpyrites. The product contained 15.04% of boron, 1.09% 01' aluminum,0.02% of sulphur, with the remainder substantially all iron. 01

the boron contained in the crude'ierroboron,

85% was recovered mtne refined alloy.

A further example is the following: 100 pounds ofcrude chromium-boroncontaining 23.25% of boron, 8.97% of aluminum, and the remainder chieflychromiu'mywas smelted in an electric furnace together with -47 pounds ofchromiumb0ron alloy, recoveries in refined alloy of as much as 90% ofthe boron contained in the crude alloy and of 86% of the chromiumcontained in the crude alloy and in the sulphide have beenoobtained.

I claim:

Method for removing a preponderant proportion of the aluminum from analloy containing upwards of about 20% boron, upwards of about 8%aluminum, and the remainder metal of the group consisting 01' iron andchromium, which comprises melting said alloy and treating the melt witha sulfide of a metal of said group consisting of iron and chromium.

AUGUST M. KUHLMANN.

